1. Field of the Invention
The present invention relates to a roaming service using a mobile terminal. More particularly, the present invention relates to a Home Public Land Mobile Network (PLMN) search method of a mobile terminal for rapidly performing a location registration in a Home PLMN or preferred roaming network by a touch on a touch screen of the mobile terminal when frequent movement through border areas sharing borders occurs.
2. Description of the Related Art
With the rapid globalization of the mobile industry, roaming contracts are made between providers of many countries. Accordingly, the user can receive a service that enables the user to use his/her own terminal with a Universal Subscriber Identity Module (USIM) or Subscriber Identity Module (SIM), without any change, even when the user has moved into another country. Such a service is called a “roaming service.” The roaming service enables a subscriber to use a mobile communication service in an authorized network only if the subscriber has a legal International Mobile Subscriber Identity (IMSI).
A communication terminal receiving such a roaming service stores information on a Home Public Land Mobile Network (PLMN) to which the corresponding subscriber has joined and information on a last registered PLMN in which the communication terminal has been last used in a USIM or SIM. When the communication terminal is powered on, the communication terminal acquires a system information message using a frequency of a maximum reception strength, extracts PLMN information from the system information message, and compares the extracted PLMN information with the last registered PLMN information. When the extracted PLMN information is not identical to the last registered PLMN information, the communication terminal recognizes that the current state is a state in which international roaming is required, and performs a location registration procedure for a base station of an adjacent cell using the extracted PLMN information, so that the communication terminal receives an international roaming service.
However, upon performing the roaming service between European countries sharing borders, whenever a communication terminal enters a Home PLMN or a mobile communication network roaming-agreed with the Home PLMN, it is necessary to ensure a period of time to search for the Home PLMN information and last registered PLMN information. As a result, frequent movement through border areas increases roaming charges.
In addition, when the user attempts to forcibly change a location registration through a menu in order to reduce the roaming charges, the user must click many times in order to execute a corresponding function due to a large number of entries in the menu. Therefore, the procedure of allowing the user to directly change a location registration using a menu also has a problem in that unnecessary time consumption occurs.